Genset engines that run on liquefied petroleum gas (LPG) in a carbureted fuel system are known. Genset engines that operate with open loop EFI systems are known to run on gasoline or ethanol but are not known to run on LPG or any gaseous fuel. Therefore, it is not known to run a genset engine integrating an open loop EFI with gaseous fuels.
Fuel injection systems mix fuel with air in internal combustion engines. Fuel is forcibly pumped through an injector and the fuel is then mixed with air and is either indirectly or directly placed in the combustion chamber. The air-to-fuel ratio (AFR) must be precisely controlled to achieve desired engine performance, emissions, and fuel economy. Fuel injection systems react to changing inputs, where the data is provided by various sensors, by controlling the amount of fuel injected.
A known open loop electronic fuel injection (EFI) system uses gasoline or ethanol as its fuel, but not gaseous fuels, e.g. liquefied propane gas. Such known open loop EFI systems often include a fuel injector, an electronic control unit (ECU), an air flow sensor, a fuel pump, a fuel pressure regulator, and perhaps other input sensors. Features of the engine system include an exhaust system, an intake system, the engine, and a gas tank. Air flow enters at the intake system and exhaust flow exits at the exhaust system. An air flow sensor senses the mass of air that flows past it and transmits this data to the ECU. The ECU uses this air flow information with the requested air-to-fuel ratio (AFR), which is a value set in the software, which will provide the best engine performance, to determine the fueling needed. The ECU electrically actuates the fuel injector so that fuel mixes with the air flow to reach the AFR determined by the ECU.
FIGS. 1A and 1B show current gaseous fuel systems 10 that use carbureted fuel systems, such as in recreational vehicle settings. The fuel is stored in a liquid state in a tank 12 or in multiple tanks, e.g., a propane tank. The fuel is converted to a vapor as it leaves the tank and the fuel vapor travels from the tank 12 to a 2-stage converter/regulator 14 where the pressure of the fuel vapor is reduced, generally to about 0.4 psi. From the converter/regulator 14, the fuel vapor is provided to the appropriate appliance 16 or genset engine 18 within the recreational vehicle. As shown in FIG. 1A, there can be one converter/regulator 14 for all appliances 16 and the genset engine 18 with fuel lines that tap off of the secondary fuel line 22 to the appliances 16 and the genset engine 18. Or, as shown in FIG. 1B, there can be a separate converter/regulator 14 provided for each appliance 16 and genset engine 18 with fuel lines that tap off of the main fuel line 20 to each converter/regulator 14. In current genset engine systems, the fuel vapor is mixed with air and this air/fuel mixture is fed to a carburetor which supplies the mixture into the genset engine 18 for combustion. The problem with this is that there is no indication that the air/fuel mixture is at the correct AFR ratio to run the genset engine, which has a narrow band of AFR for operation. There is not an inexpensive device at present to accurately account for changes in the air pressure and temperature when dealing with gaseous fuels in genset engines.
Rather, genset engines that run on gasoline, ethanol, and gaseous fuels are known to operate with closed loop EFI systems. For example, genset engines that run on LPG in a carbureted fuel system are known. Engines that operate with open loop EFI systems are known to run on gasoline or ethanol, but are not known to run on liquefied petroleum gas (LPG) or any gaseous fuel. In particular, open loop EFI genset engines that run on gaseous fuels are not known.